There were few studies on unfrozen water in frozen soils under 0°C. In order to investigate the relation between unfrozen water and characteristics of frozen soils, unfrozen water contents were measured by the calory metre and calculated by using the specific surface. On Toyoura standard sand and Kaolinite, the measured values were compared with caluculated ones. As the results, it became clear that when the temperature fell the unfrozen water contents decreased and the compressive strength increased.